Should a lumbar puncture (LP) be performed in an 11-month-old with a febrile seizure?

Lumbar Puncture in an 11-Month-Old with Febrile Seizure

In an 11-month-old child presenting with a febrile seizure, lumbar puncture is almost always indicated to rule out bacterial meningitis, as children under 12 months are at highest risk and clinical signs of meningitis may be subtle or absent at this age. 1, 2

Age-Specific Risk Assessment

The critical factor here is age. Children under 12 months represent a distinct high-risk population:

• Lumbar puncture should be performed in infants younger than 12 months with febrile seizures because meningitis symptoms are not specific in this age group and the risk of missing bacterial meningitis is unacceptable 3, 1, 4

• The 11-month-old falls into the highest-risk category where LP is "almost always indicated" according to current guidelines 1, 2

• Children younger than 12 months at their first febrile seizure have approximately 50% probability of recurrent febrile seizures, but more importantly, they are at increased risk for serious bacterial infections including meningitis 3

When LP is Mandatory vs. Optional

Mandatory indications for LP include:

• Age less than 12 months (your patient qualifies) 3, 1, 2
• Signs of meningism present 3, 1
• Complex seizure (prolonged >15 minutes, focal features, or multiple seizures in 24 hours) 3, 5
• Child excessively drowsy, irritable, or systemically ill 3, 1
• Incomplete recovery after one hour 3, 1
• Prior antibiotic treatment (which can mask meningitis symptoms) 5, 4

LP may be deferred only if ALL of the following are present:

• Age >12 months (your patient does NOT meet this criterion) 6
• Simple febrile seizure (generalized, <15 minutes, single episode in 24 hours) 3
• Completely normal neurological examination 5, 6
• No signs suggestive of CNS infection 5, 6
• Fully immunized against Haemophilus influenzae and Streptococcus pneumoniae 1

Evidence Supporting LP in This Age Group

Recent high-quality studies have attempted to challenge routine LP in young infants, but the data still supports performing LP at 11 months:

• A 2015 French multicenter study of 205 children aged 6-11 months with first simple febrile seizure found zero cases of bacterial meningitis (0%, 95% CI: 0-2.2%), but the upper confidence interval of 2.2% still represents an unacceptable risk given the devastating consequences of missing meningitis 6

• A 2013 French study found bacterial meningitis incidence of 1.9% in children under 18 months with febrile seizures, with all cases occurring in those with complex seizures or other clinical signs 5

• A 2010 Tunisian study found 10% of infants under 12 months with febrile seizures had bacterial meningitis, with age ≤7 months being a significant predictor (p=0.035) 7

• A 2009 Pakistani study found 4.7% of children with fever and seizure had meningitis, with age <12 months being a significant risk factor, and concluded LP is mandatory in infants younger than 12 months 4

Critical Clinical Pitfalls to Avoid

• Do not assume a "simple" febrile seizure rules out meningitis in an 11-month-old - bacterial meningitis can present with a brief, generalized seizure as the only manifestation 4

• Do not delay LP while waiting for the child to "wake up" - if the child remains drowsy or has altered mental status, this is an additional indication for immediate LP 3, 1

• Do not skip LP based solely on vaccination status - while Hib and pneumococcal vaccines have reduced meningitis incidence, they do not eliminate the risk, and other pathogens remain possible 1, 5

• Ensure the child is not comatose before performing LP due to risk of herniation - brain imaging may be necessary first if there are concerns for increased intracranial pressure 3

Practical Management Algorithm

1. Measure blood glucose immediately with glucose oxidase strip if child is still convulsing or unrousable 3, 1

2. Assess for contraindications to LP (signs of increased intracranial pressure, hemodynamic instability) 3

3. Perform LP in this 11-month-old unless there are specific contraindications 1, 2

4. Do NOT routinely order EEG, extensive metabolic panels, or neuroimaging for simple febrile seizures 3, 8

5. Hospitalize for observation if LP is deferred for any reason, with plan to reassess within hours 3, 7

What NOT to Do

• Do not order routine EEG, blood urea, serum electrolytes, or serum calcium - these are not indicated for simple febrile seizures 3

• Do not start prophylactic anticonvulsant therapy - neither continuous nor intermittent anticonvulsant therapy is recommended for simple febrile seizures due to risks outweighing benefits 3, 2

• Do not rely on antipyretics to prevent seizure recurrence - they are ineffective for this purpose, though paracetamol should be given for comfort 3, 2